This invention relates generally to the field of collapsible reusable shipping containers particularly suited for shipping liquids and particulate materials using a foldable baglike inner container. Devices of this general type are known in the art, and the invention lies in specific constructional details which permit improved ease of assembly and disassembly, reduction in manufacturing costs, and a reduction in overall size in collapsed condition which has heretofore been unobtainable.
In my prior U.S. Pat. No. 4,663,207, granted Aug. 17, 1986 under the title Reinforcing Element for Collapsible Containers, there is disclosed a foldable unit for use with single ply or multiple ply corrugated containers. The insert in folded condition is disposed with the folded container with which it is used to, therefore, require very little additional storage space. The insert element is constructed to include inner and outer walls. The outer walls fold along vertical generally medially disposed fold lines. The inner walls are laminated to the inner surface of the outer walls on one side of the fold lines to prevent folding in only a single direction, and are provided with foldable narrow flaps, the fold lines of which are disposed in the corners of the insert when the element is in assembled or erected condition. Using materials commensurate with the overall size of the container and the expected compressive loads, the result is a collapsible container of strength far in excess of that normally expected in conventional collapsible container construction.
Certain types of cargo are not subject to damage by breakage or crushing due to externally applied forces. Liquids and particulate cargos, in particular, are usually damaged as a result of leakage, spoilage, and the like. For such goods, the prime consideration is resistance to internal pressure caused by the weight of the load resulting in bulging, and potential leakage caused by damage to the container. While such containers require capability to resist compressive forces, the compression is usually the result of stacking containers in loaded condition, one upon another. When such cargos are shipped in containers with separate liner elements, the result is excess cost of manufacture, unneeded and unnecessary shipping weight, and greater-than-necessary storage volume when the container is in collapsed condition.